Proteins Prez
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Transcript of Proteins Prez
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Proteins are a class of ubiquitous macromolecules in
all organisms.The Importance is implied in the nameproteioswhichmeans"firstplaceinGreek.
Theyplayaroleinalmostallprocessesinthebodyincluding:
OxygentransportGeneRegulation
Celltocellrecognition
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TypeofProtein Function Examples
Transport Proteins Transportsubstancesacrossmembranes
Ionchannel,Atpasepumps
Storage Proteins Storageandreleaseofaminoacids
Seedproteinsbrokendownduringgermination
Enzymes Catalyst hydrolyzes
Structural Proteins Supportcellularstructures Collageninconnectivetissue:keratininhairandnails
Regulatory Proteins Regulatecellularfunctions Transcriptionfactorsthatbind
toDNAandregulateexpression
Motility Proteins Movementofthecell Actinandmyosininmuscles;tublininciliaandflagella
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TheMonomersareAminoAcidsProteins are made from a linear sequence of amino
acids.
There are 20 amino acids that are used in thesynthesis ofproteins.
Every amino acid has the same basicstructure.They carry and amino group, a hydrogenatom, and a side chain know as the R group. All are
attached to a central carbon atom know as thealpha carbon.
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ThemonomersareAminoAcids
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AminoAcidsThecentralcarbonisasymmetricinallaminoacids
exceptforglycinewhichhasahydrogenasanRgroupandthereforecanexistintwoisomericformscalledLandD-aminoacids.BothformsexistinnaturebutonlyL-aminoacidsoccurinproteinsynthesis.
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Zwi2erions
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AminoAcidsAll20aminoacidshavecommonstructurebutdifferin
theirRgroup.Therefore,thechemicalnatureoftheaminoacidscomefortheRgroup.
9ofthisaminoacidshavenonpolarRgroupsandarethereforehydrophobic.Theseareusuallyfoundintheinteriorofthecellandwillbeexcludedfromtheaqueousenvironmentandwillinsteadbefoundinhydrophobiclocationssuchastheinteriorofamembrane.
Theremaining11aminoacidsarehydrophilic,witheitherpolarorchangedRgroups.Hydrophilicproteinstendtooccuronthesurfaceofproteins,therebymaximizingtheirinteractionswithwaterandotherchargedsubstances.
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Polyped7deForma7onPolypeptidesareformedbycovalentbondingbetweenaminoacids.Theprocessinvolvestheadditionofanewaminoacidtothechainbythedehydration/condensationreactions.ThecovalentC-Nbondlinkningthe2aminoacidsisknownasaPeptide
bond.
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Polypep7deForma7onTheformationofthepolypeptidehasdirectionality.It
alwayshasanaminogroupatoneendcalledtheNterminusandtheotherendhasacarboxylgroupcalledtheCterminus.
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LevelsofOrganiza7on
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PrimaryStructureTheprimarystructureofaproteinisasequenceof
aminoacidslinkedtogetherbypeptidebonds,formingapolypeptide.
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SecondaryStructureTheSecondarystructureinvolvesregionsofthe
polypeptidebeingassociatedtogetherbyH-bonds.Thecancoilintoahelixorformpleatedsheets.
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Ter7aryStructuresTheTertiarystructureisformedwhenregionsthesecondarystructureassociateduetodisulphide,ionic
andH-bondsorvanderwaalsandhydrophobicinteractions.Theseassociatesresultintheformation
ofa3Dstructure.
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QuaternaryStructuresTheQuaternaryStructureistheassociationof
multiplepolypeptidestoformafinalfunctionalprotein.
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Denatura7onofProteins Iftheproteinisexposedtodenaturingconditionse.g.
increaseintemp.orpH,thisdisruptsnoncovalentinteractionsbetweenaminoacidRgroupsandmakestheproteininactive.
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Renatura7on
Oncetheproteinisremovedfromtheextremeconditions,ThisallowsforrenewedinteractionsbetweentheRgroups.Thepolypeptidespontaneouslyreturnstoitsnativeconformationandregainsitsactivity.
Thesuggestthattheaminoacidsequencehasalltheinformationneededforthefoldingofthepolypeptide
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ProteinSynthesis
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GenesCodeforAminoAcidsThenucleotidesequenceofDNAwilldictatetheaminoacidsequenceofaprotein
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SickleCell
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SickleCellThisdiseaseoccurswhenGlutamate(Glu)ofthe
normalhemoglobinisreplacedbyValine(Val).Thiscausesthecelltobecomesickleandmorerigid.
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SickleCell
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OtherImportantProteinsHemoglobin
Hemoglobinistheiron-containingoxygen-transport
metalloproteinintheredbloodcells.Hemoglobininthebloodcarriesoxygenfromtherespiratoryorganstotherestofthebody(i.e.thetissues)whereitreleasestheoxygentoburnnutrientstoprovideenergytopowerthefunctionsoftheorganism,andcollectstheresultantcarbondioxidetobringitbacktotherespiratoryorganstobedispensedfromtheorganism.
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ImportantProteinsHemoglobin
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OxygenBindingCurveFetalHbhasahigheraffinitythanmaternalHb